Cable or radio wave-based receiver devices (the television tuner is a typical example) convert the frequency of signals received, for example, via an antenna to IF (Intermediate Frequency) frequency (intermediate frequency, center frequency) suitable to the broadcasting system in a particular country or region, to supply signals with desirable frequencies to either a demodulator circuit for analog television broadcast or a demodulator circuit for digital television broadcast. The desirable frequencies are generally about 30 MHz to 60 MHz although the IF frequencies vary depending on the country or region in which the receiver device is being used.
There is conventional technology, as disclosed in, for example, U.S. Patent Application 2006/0083335 (published Apr. 20, 2006; hereinafter “patent literature 1”), that builds up the receiver device from semiconductor devices, in other words, from a combination of analog and digital circuits provided on a semiconductor substrate.
FIG. 5 is a schematic block diagram of a conventional receiver device. FIG. 5 shows the configuration of the receiver device disclosed in patent literature 1 as an exemplary configuration of the conventional receiver device.
The receiver device shown in FIG. 5 includes an input terminal 401, a variable gain low noise amplifier (typically called VGLNA) 402, frequency converters 403 and 404, filters 405 and 406 composed of analog circuitry (“analog filters”), AD converters (analog-to-digital converters) 407 and 408, filters 409 and 410 composed of digital circuitry (“digital filters”), frequency converters 411 and 412, an adder 413, and a DA converter (digital-to-analog converter) 414.
An analog filter 415, a variable gain low noise amplifier 416, and an output terminal 417 are connected in series in this order following the receiver device shown in FIG. 5, that is, to an output terminal (not shown) of the DA converter 414.
In the receiver device shown in FIG. 5, parts of the AD converters 407 and 408 (those parts which process digital signals), the digital filters 409 and 410, the frequency converters 411 and 412, the adder 413, and a part of the DA converter 414 (that part which processes digital signals) constitute the digital circuit section 400 which processes digital signals.
The receiver device shown in FIG. 5 operates as in the following to implement various signal processes on incoming signals in a simple and convenient manner.
For example, as an analog signal (reception signal) received by an antenna (not shown) is fed at the input terminal 401 to the low noise amplifier 402, the low noise amplifier 402 amplifies the reception signal for output to the frequency converters 403 and 404.
The frequency converter 403 converts the frequency of the signal fed from the low noise amplifier 402 to a frequency suitable for the various signal processes for output to the analog filter 405. Likewise, the frequency converter 404 converts the frequency of the signal fed from the low noise amplifier 402 to a frequency suitable for the various signal processes for output to the analog filter 406.
The “frequency suitable for the various signal processes” refers to, for example, either a baseband frequency or a Low-IF (Low-intermediate frequency) frequency. The baseband frequency is the frequency of the signal obtained by such direct frequency conversion (baseband signal) that the IF frequency can be 0 Hz. The Low-IF frequency is the frequency of the signal obtained by such Low-IF frequency conversion that the IF frequency can be about 2 MHz to 4 MHz.
The frequency converters 403 and 404 are, for example, known multipliers which carries out frequency conversion of an input signal by mixing the signal with a local oscillation component generated by a local oscillator circuit (not shown).
The analog filter 405 removes unnecessary frequency components (interference) from the signal supplied from the frequency converter 403 for output to the AD converter 407. Similarly, the analog filter 406 removes unnecessary frequency components (interference) from the signal supplied from the frequency converter 404 for output to the AD converter 408.
The AD converter 407 converts the signal supplied from the analog filter 405 from analog to digital for output to the digital filter 409. Similarly, the AD converter 408 converts the signal supplied from the analog filter 406 from analog to digital for output to the digital filter 410.
The digital filter 409 removes unnecessary frequency components (interference) from the digital signal supplied from the AD converter 407 for output to the frequency converter 411. Likewise, the digital filter 410 removes unnecessary frequency components (interference) from the digital signal supplied from the AD converter 408 for output to the frequency converter 412.
The frequency converter 411 converts the digital signal supplied from the digital filter 409 from the IF frequency to the desirable frequency (about 30 MHz to 60 MHz) mentioned above for output to the adder 413. Likewise, the frequency converter 412 converts the digital signal supplied from the digital filter 410 from the IF frequency to the desirable frequency for output to the adder 413.
The adder 413 adds up the digital input signals from the frequency converters 411 and 412 for output to the DA converter 414.
The DA converter 414 converts the signal supplied from the adder 413 from digital to analog for output to the analog filter 415.
The analog filter 415 removes unnecessary frequency components (interference) from the analog signal supplied from the DA converter 414 for output to the low noise amplifier 416. The low noise amplifier 416 amplifies the analog signal supplied from the analog filter 415 for external output via the output terminal 417.
In the receiver device shown in FIG. 5, the frequency converters 403 and 404 and the frequency converters 411 and 412 convert the frequency of the reception signal to implement various signal processes on the reception signal in a simple and convenient manner. The receiver device shown in FIG. 5 then supplies the signal obtained by the frequency conversion in the frequency converters 411 and 412 to a demodulator circuit.